powerpc: allow ioremap within reserved memory regions

Add a flag to let a platform ioremap memory regions marked as reserved.

This flag will be used later by the Nintendo Wii support code to allow
ioremapping the I/O region sitting between MEM1 and MEM2 and marked
as reserved RAM in the patch "wii: use both mem1 and mem2 as ram".

This will no longer be needed when proper discontig memory support
for 32-bit PowerPC is added to the kernel.

Signed-off-by: Albert Herranz <albert_herranz@yahoo.es>
Acked-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Grant Likely <grant.likely@secretlab.ca>

arch/powerpc/mm/init_32.c

@@ -82,6 +82,11 @@ extern struct task_struct *current_set[NR_CPUS];
 int __map_without_bats;
 int __map_without_ltlbs;
 
+/*
+ * This tells the system to allow ioremapping memory marked as reserved.
+ */
+int __allow_ioremap_reserved;
+
 /* max amount of low RAM to map in */
 unsigned long __max_low_memory = MAX_LOW_MEM;
 

arch/powerpc/mm/mmu_decl.h

@@ -115,6 +115,7 @@ extern void settlbcam(int index, unsigned long virt, phys_addr_t phys,
 extern void invalidate_tlbcam_entry(int index);
 
 extern int __map_without_bats;
+extern int __allow_ioremap_reserved;
 extern unsigned long ioremap_base;
 extern unsigned int rtas_data, rtas_size;
 

arch/powerpc/mm/pgtable_32.c

@@ -26,6 +26,7 @@
 #include <linux/vmalloc.h>
 #include <linux/init.h>
 #include <linux/highmem.h>
+#include <linux/lmb.h>
 
 #include <asm/pgtable.h>
 #include <asm/pgalloc.h>
@@ -191,7 +192,8 @@ __ioremap_caller(phys_addr_t addr, unsigned long size, unsigned long flags,
 	 * Don't allow anybody to remap normal RAM that we're using.
 	 * mem_init() sets high_memory so only do the check after that.
 	 */
-	if (mem_init_done && (p < virt_to_phys(high_memory))) {
+	if (mem_init_done && (p < virt_to_phys(high_memory)) &&
+	    !(__allow_ioremap_reserved && lmb_is_region_reserved(p, size))) {
 		printk("__ioremap(): phys addr 0x%llx is RAM lr %p\n",
 		       (unsigned long long)p, __builtin_return_address(0));
 		return NULL;